Pressure-sensitive adhesive based on ethylenically-unsaturated α-olefin polymer cured with hydrosilane

ABSTRACT

A pressure-sensitive adhesive that can adhere aggressively to both polar and nonpolar substrates and has good internal strength at high temperatures is provided by heat or radiation curing a blend of an ethylenically-unsaturated α-olefin polymer, a crosslinker having at least 2 hydrosilyl groups, and a hydrosilation catalyst. A preferred hydrosilane crosslinker has the formula ##STR1## wherein R is an alkyl group having 1-6 carbon atoms, and n&#39; is a number in the range of 2 to 35.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to pressure-sensitive adhesives that have goodinternal strength at high temperatures. The invention also relates topressure-sensitive adhesives that can be coated without evolution oforganic matter to provide tapes which are substantially odor-free andphysiologically inert.

2. Description of the Related Art

When considering adhesive tapes, pressure-sensitive adhesive (PSA) tapesare the easiest to use, but for the most part, pressure-sensitiveadhesives do not adhere well to nonpolar substrates. Another problem isthat most PSAs are unsuited for uses requiring good internal strength atelevated temperatures. For example, rubber-resin PSAs tend to soften anddegrade when heated. PSAs based on styrene-containing block copolymersalso do not retain good internal strength when heated, because styrenehas a low T_(g) and so softens at moderately elevated temperatures.Acrylate PSAs tend to give off toxic vapors at elevated temperatures.They typically contain monomeric materials which, even at ordinary roomtemperatures, exude odors that make acrylate PSA tapes generallyunsuitable for medical uses. Polyisobutylene PSAs are often used formedical uses because they are physiologically inert, but they tend to bedeficient in internal strength.

Of known PSAs, silicones best retain high internal strength at elevatedtemperatures, but known silicone PSAs must be coated from organicsolvents. Typically, a metal catalyst is employed to initiate a reactionbetween gum and resin components, especially when good internal strengthat elevated temperatures is required. Most effective are tin catalysts,the toxic nature of which prevents the resulting PSAs from being used inmany important applications such as those involving food or medicalneeds. In spite of such problems and their high price, silicone PSAtapes are used where good internal strength at high temperatures is ofutmost importance, e.g., as electrical insulating tapes and as maskingtapes for use with paints to be baked at high temperatures.

PSAs can be based on α-olefin polymers. For example, U.S. Pat. No.3,635,755 (Balinth et al.) describes PSAs made from homopolymers of C₆to C₁₁ α-olefins or from interpolymers of C₂ to C₁₆ α-olefins. Thesetapes are said to show substantially no irritation to skin and to havelow shear adhesions that facilitate non-irritating removal from humanskin.

After noting that prior PSAs based on α-olefin polymers had very poorcohesive (internal) strength, U.S. Pat. No. 3,954,697 discloses thatPSAs provided by copolymers of polypropylene and C₆ to C₁₀ α-olefins canbe hot-melt coated at a melt temperature of at least 350° F. (177° C.)so that the copolymers exhibit no detectable crystallinity by eitherX-ray or DSC techniques. Nothing is said about cohesive strengths atelevated temperatures.

U.S. Pat. No. 4,288,358 (Trotter et al.) says that a PSA adhesive basedon α-olefin polymers can be hot-melt coated and can have good resistanceto shear adhesion failure, i.e., good internal strength. This isaccomplished by blending at least one C₆ to C₁₀ linear α-olefin polymerwith a plasticizing oil and a tackifying resin. Nothing is said aboutinternal strength at elevated temperatures.

Another publication of PSAs based on α-olefin polymers is U.S. Pat. No.3,542,717.

U.S. Pat. No. 4,178,272 discloses that a hot-melt adhesive whichprovides strong T-peel and lap shear bonds can be made using α-olefinpolymers. The hot-melt adhesive disclosed in this reference is a blendof poly(propylene-co-higher 1-olefin), tackifying resin, and crystallinepolypropylene. The blend is not said to be tacky or a PSA. In Example 1,the bonds are made at 200° C.

UK Pat. Specification No. 1,188,327 discloses a terpolymer of ethylene,propylene, and a di-unsaturated unconjugated olefin which can becrosslinked with an organopolysiloxane to provide an elastomer.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a pressure-sensitive adhesivecomposition comprising a curable blend of (a) an α-olefin polymercontaining ethylenic unsaturation, (b) a crosslinker having at leasthydrosilyl groups, and (c) a hydrosilation catalyst. Thepressure-sensitive adhesive has good internal strength at elevatedtemperatures while avoiding the aforementioned problems. Because ofthis, the novel PSA can be useful for medical or surgical tapes, andautomotive masking tapes and other tapes requiring good strength atelevated temperatures. The composition can be cured by heat orradiation.

Advantages of the novel PSA include

1) being odor-free,

2) being physiologically inert and hence non-allergenic, and

3) having the ability to adhere aggressively to both polar and nonpolarsubstrates.

Furthermore, large-scale production can produce the novel PSA and PSAtapes at costs comparable to that of any major PSA now on the market.

The PSA of the invention comprises a heat or radiation curablecomposition which is a PSA both before and after being cured.

In this application:

"alpha-olefin polymer" means a polymer prepared by polymerization of atleast one alpha-olefin monomer;

"Ziegler-Natta (Z-N) catalyst" means a two-component coordinationinitiator or catalyst having the properties described by Seymour andCarraher, "Polymer Chemistry", Marcel Dekker, Inc., N.Y. (1988) p. 296.The preferred catalyst systems are dialkyl aluminum chloride/titaniumtrichloride and dialkyl aluminum sesquichloride/vanadium oxytrichloride,which are commercially available.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferably, the ethylenically-unsaturated α-olefin polymer of the PSAcomposition has the formula: ##STR2## wherein:

x, y, and z are numbers designating the relative molar amounts of M¹,M², and M³ units that are randomly located in the backbone chain of thepolymer such that the polymer has a weight average molecular weight inthe range of 30,000 to 3.5 million, x is at least 60 mole % of x+ywherein y can be zero, and z is 0.1 to 10 mole % of x+y+z;

M¹ is an ethanediyl repeat unit having a pendent hydrocarbyl grouphaving 4 to 12 carbon atoms;

M², when present, is different from M¹, and is an ethanediyl repeat unitselected from 1) ethylene, 2) units having a pendent hydrocarbyl groupselected from linear and branched alkyl groups having 1 to 18 carbonatoms, cyclic alkyl groups and aryl groups having 5 to 18 carbon atoms,and 3) 1,2-cyclopentylene and 1,2-cyclohexylene groups having 5 to 18carbon atoms; and

M³ is an ethanediyl repeat unit having a pendentethylenically-unsaturated aliphatic or aryl group selected from thegroup consisting of 1) linear and branched mono- andpolyethylenically-unsaturated hydrocarbyl groups having 3 to 18 carbonatoms, 2) cyclic mono- and polyethylenically-unsaturated aliphaticgroups optionally containing at least one of oxygen and nitrogenheteroatoms, the groups having 5 to 18 carbon atoms, 3) aryl groupssubstituted by mono- or polyethylenically-unsaturated groups having atotal of 7 to 18 carbon atoms, and 4) cycloalkenylene groups having 6 to18 carbon atoms wherein the cyclic group has at least 6 carbon atoms inthe ring, provided that the ethylenically-unsaturated (C═C) moiety isnot bonded directly to a backbone carbon atom.

Most preferably, the ethylenically-unsaturated α-olefin random polymerhas the formula: ##STR3## wherein

R¹ is an alkyl group having 4 to 12 carbon atoms, preferably 4 to 8carbon atoms, and most preferably 4 to 6 carbon atoms;

R² is hydrogen or a hydrocarbyl group, preferably selected from linearand branched alkyl groups having 1 to 18 carbon atoms, cyclic alkylgroups having 5 to 18 carbon atoms, and aryl groups having 6 to 12carbon atoms;

R³ is hydrogen or R³ together with R² and the carbon atoms to which theyare attached forms a saturated monocyclic or polycyclic ring systemhaving 5 to 20 carbon atoms, wherein at least 5 carbon atoms are in thering system; preferably R³ is hydrogen;

x, y, z' and z" are numbers designating the relative molar amounts ofmonomer units comprising the backbone chain of the polymer such that thepolymer has a weight average molecular weight in the range of 30,000 to3.5 million, x is at least 60% of x+y wherein y can be zero, and z'+z"is 0.1 to 10% of x+y+z' and z", and either of z' or z" can be zero; z ofFormula I equals the sum of z'+z" of Formula II;

R⁴ is an unsaturated aliphatic hydrocarbyl group having 3 to 18 carbonatoms, the unsaturated group of which is separated from the ##STR4## ofthe α-olefin polymer backbone by at least atom, preferably selected fromlinear and branched alkenyl groups having 3 to 18 carbon atoms,non-conjugated polyethylenically-unsaturated aliphatic groups having 6to 18 carbon atoms, cyclic alkenyl groups having 5 to 18 carbon atoms,and cyclic non-conjugated polyethylenically-unsaturated groups having 6to 18 carbon atoms;

R⁵ is hydrogen or R⁵ together with R⁴ and the carbon atoms to which theyare attached forms an unsaturated or non-conjugated polyunsaturatedmonocyclic ring system having 6 to 20 carbon atoms, the unsaturatedgroups of which are separated from the ##STR5## of the α-olefin polymerbackbone by at least one carbon atom;

R⁶ is a linear or branched alkyl group having 1 to 18 carbon atoms orcyclic alkyl group having 5 to 18 carbon atoms; and

R⁷ is a linear or branched ethylenically- or non-conjugatedpolyethylenically-unsaturated aliphatic hydrocarbon group having 3 to 18carbon atoms, or a cyclic ethylenically or non-conjugatedpolyethylenically-unsaturated aliphatic hydrocarbyl group having 5 to 18carbon atoms.

It is to be understood that the α-olefin polymers of the invention haveterminating groups, the identity of which depends upon the catalyst andcomponents in the polymerizing composition. The terminating groups,because of their insignificant concentration, do not affect theessential properties of the polymers.

When R¹ contains from 4 to 8 carbon atoms, the ethylenically-unsaturatedα-olefin polymer is a tacky PSA at ordinary room temperatures (20° to25° C.). When R¹ contains from 9 to 12 carbon atoms, theethylenically-unsaturated α-olefin polymer is not normally tacky butbecomes tacky when heated to moderately elevated temperatures (above 25°C. to 100° C.) and normally loses that tackiness when cooled to ambienttemperature (20° to 25° C.). While tacky, it can form strong bonds underfingertip pressure. When R¹ contains from 9 to 12 carbon atoms and R² isan alkyl group of from 1 to 8 carbon atoms, theethylenically-unsaturated α-olefin polymer may be slightly tacky atordinary room temperatures. For some uses, the ability of a PSA tobecome tacky only when heated is an important advantage.

The preferred ratio of x and y groups to z groups is from 20:1 to 200:1(0.5 to 5 mole %). As that ratio increases, theethylenically-unsaturated α-olefin polymers have increased tackiness,but as that ratio decreases, they have increased internal strength.Hence, that ratio can be selected to afford the desired balance oftackiness and cohesive strength. For most uses, the best balance isattained when the ratio is between 30:1 and 100:1 (0.3 to 3.2 mole %).Tackiness can also be increased, or an otherwise non-tackyethylenically-unsaturated α-olefin polymer of the invention can be madetacky, by blending it with tackifying resin.

Preferably, the ethylenically-unsaturated α-olefin polymer has a T_(g)not higher than 0° C., more preferably not higher than -20° C., and itsT_(g) can be as low as -60° or -70° C. A PSA ethylenically-unsaturatedα-olefin polymer that has a low T_(g) tends to have superior adhesion.Furthermore, an ethylenically-unsaturated α-olefin polymer with a lowerT_(g) can be blended with larger amounts of tackifying resin to makecoatings that exhibit less shocky peel adhesion.

The ethylenically-unsaturated α-olefin polymer has an inherent viscosity(IV) in toluene in the range of 0.5 to 5 dl/g, preferably in the rangeof 0.5 to 3 dl/g, which values roughly correspond to average molecularweights of from 50,000 to 10,000,000, preferably 50,000 to 3,500,000,respectively. At an IV substantially below that preferred range, theethylenically-unsaturated α-olefin polymer can be less likely to attainhigh internal strength, especially at elevated temperatures. Atviscosities substantially higher than 3 dl/g, theethylenically-unsaturated α-olefin polymer preferably is coated fromsolution. At an IV above 5 dl/g, it may be necessary to employ asolution that is too dilute to be commercially practical.

Useful crosslinkers containing at least two hydrosilyl groups include:##STR6## wherein

each R is an alkyl group having 1-6 carbon atoms or a phenyl group;

each R' is the same as R or hydrogen;

Y is oxygen, or an arylene group having 6 to 16 carbon atoms, analyklene group having 2 to 16 carbon atoms, or (CF₂)_(d) where d is aninteger from 2 to 10; each m, n and p is 0 or a number in the range of 1to 35 designating the relative molar amount of m, n and p; and

at least two R' groups are hydrogen.

Specific classes of these crosslinkers are hydrosiloxanes (1) through(5) ##STR7## wherein n' is a number from 2 to 35, and R is as definedabove, and preferably R is methyl; ##STR8## wherein m' is at least one,n' is a number from 2 to 35, and R is as defined above, and preferably Ris methyl; ##STR9## wherein p' is a number from 2 to 35, and R and Y areas defined above, and preferably R is methyl; ##STR10## wherein m is 0or a number up t 35, and R is as defined above, and preferably R ismethyl; and ##STR11## wherein R and Y are as defined above, andpreferably R is methyl.

Other useful crosslinkers include silica particles having adsorbed ontotheir surfaces compounds having at least two dimethylhydrosilyl groups;e.g., compound (4) or (5) above can be adsorbed onto silica particles.

The preferred concentration of crosslinker (b), having at least 2hydrosilyl groups, is in the range of 1-20 parts per hundred (phr) ofethyleneically-unsaturated α-olefin polymer component (a), morepreferably in the range of 1-5 phr.

Hydrosilation catalysts are well-known in the art and include boththermal and photoactivated catalysts such as platinum complexesdisclosed in U.S. Pat. Nos. 4,228,345 and 4,510,094, which are herebyincorporated by reference, and rhodium complexes disclosed in Faltynek,"Inorganic Chemistry", 20(5), pp. 1357-1362 (1981). Platinum complexesafford a faster reaction and hence are preferred. Usefulplatinum-containing catalysts include, for example,

chloroplatinic acid,

chloroplatinic acid-olefin complexes,

chloroplatinic acid-vinylsiloxane complexes,

(η⁵ -cyclopentadienyl)trimethylplatinum,

[η⁵ -(trimethylsilyl)cyclopentadienyl]trimethylplatinum, and

platinum(II) acetylacetonate.

The catalyst can be supported or coated on a microparticulate carriersuch as alumina, silica or zirconia. The catalyst can be employed in anamount in the range from 0.1 to 1,000 ppm (parts per million of totalethylenically-unsaturated α-olefin polymer plus crosslinker), preferablyfrom 1 to 300 ppm. At substantially less than 1 ppm, the novel PSAcomposition, after being heat or radiation cured, may not have goodinternal strength at elevated temperatures. At substantially greaterthan 300 ppm, thermal curing may render the PSA nontacky. Whenplatinum-containing catalysts are used, because of the relatively highcost of a platinum-containing complex, it preferably is employed in therange of 1-100 ppm.

The ethylenically-unsaturated α-olefin polymer can be produced by thefollowing methods. In a first method, a C₆ to C₁₄ α-olefin monomer iscopolymerized with a nonconjugated linear diene having 5 to 20 carbonatoms or more, a monocyclic diene having 6 to 20 or more carbon atoms,or a polycyclic diene having 7 to 20 or more carbon atoms, using a Z-Ncatalyst to produce a copolymer containing ethylenic unsaturation. Inthe copolymer produced by this first method, M³ of formula I, has, forexample, structures such as III, IV and V (below) when the diene islinear, and VI, VII, and VIII (below) when the diene is cyclic,##STR12## wherein s is an integer from 1 to 16, preferably 2 to 4, and tis an integer from 1 to 14, preferably 2 to 4.

A second method involves the steps of:

a) polymerizing a C₆ to C₁₄ α-olefin monomer alone or with at least onelower α-olefin monomer using a Z-N catalyst to produce a saturatedhomopolymer or a copolymer,

b) reacting the resulting α-olefin polymer with maleic anhydride in thepresence of an initiator such as a peroxide and preferably an electrondonor (e.g., triphenyl phosphite or triethyl phosphate) to produce anadduct, and

c) reacting the maleated α-olefin polymer adduct with anethylenically-unsaturated primary amine or isocyanate having 3 to 20carbon atoms, either in solution or in a melt, e.g., in an extruder.

In the resulting α-olefin polymer, M³ of Formula I has structures suchas IX and X. ##STR13##

Alpha-olefins that can be used in the preparation of theethylenically-unsaturated α-olefin polymer of the invention can havefrom 2 to 20 carbon atoms. Representative examples include, but are notlimited to, ethylene, propylene, 1-butene, 1-pentene, 1-hexene,1-heptene, 1-octene, and 1-tetradecene; branched olefins such as3-methyl-1-butene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, and3-ethyl-1-pentene; cyclic olefins such as cyclopentene, cyclohexene,3-methylcyclopentene, 4-n-butylcyclohexene, bicyclo[2.2.1]hept-2-ene,1,7,7-trimethylbicyclo[2.2.1]hept-2-ene (bornylene)bicyclo[3.2.0]hept-2-ene, bicyclo[3.2.0]hept-6-ene,bicyclo[2.2.2]oct-2-ene, aend bicyclo[3.2.2]non-6-ene; and aromaticolefins such as allylbenzene, 1H-indene, 3-methyl-lH-indene, andstyrene.

Non-conjugated dienes that can be used in the preparation of theα-olefin polymer of the invention have 5 to 20 carbon atoms.Representative examples include, but are not limited to, 1,4-pentadiene,1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, and 1,13-tetradecadiene;cyclic dienes such as 1,4-cyclohexadiene, bicyclo[2.2.1]hept-2,5-diene,bicyclo[2.2.2]oct-2,5-diene, bicyclo[2.2.2]oct-2,6-diene,1,7,7-trimethylbicyclo[2.2.1]hept-2,5-diene,5-allylbicyclo[2.2.1]hept-2-ene, and 1,5-cyclooctadiene; and aromaticdienes such as bis(ω-alkenyl)benzenes such as 1,4-diallylbenzene, and4-allyl-lH-indene.

The novel PSA preferably includes a tackifying resin which imparts tack,lower viscosity, improved coatabilty, good heat stability, and improvedpeel adhesion. Compatible tackifying resins include resins derived frompolyterpenes, synthetic polyterpenes and the like. Hydrocarbontackifying resins can be prepared by polymerization of monomersconsisting primarily of olefins and diolefins and include, for example,residual by-product monomers of the isoprene manufacturing process.These hydrocarbon tackifying resins typically exhibit Ball and Ringsoftening points of from about 80° C. to about 145° C., acid numbersfrom about 0 to 2, and saponification values of less than one. Examplesof such commercially available tackifying resins based on a C₅ olefinfraction of this type are Wingtack™ 95 and Wingtack™ 115 available fromGoodyear Tire and Rubber Co. Other useful hydrocarbon tackifying resinsinclude Regalrez™ 1078 and Regalrez™ 1126 hydrocarbon tackifiersavailable from Hercules Chemical Co., Inc.

The tackifying resins may contain ethylenic unsaturation, but saturatedtackifying resins are preferred for those applications where oxidationresistance is important. The total amount of tackifying resin in thenovel PSA composition is from 0 to 150 parts, more preferably 5 to 50parts, and most preferably 10 to 35 parts by weight per 100 parts of theethylenically-unsaturated α-olefin polymer.

The novel PSA composition may also include small quantities of othermaterials commonly employed in PSA compositions, e.g., supplementaryantioxidants, pigments, inhibitors, stabilizers, and fillers.Preferably, the total amount of such other materials does not exceed 4phr.

The PSA composition of the invention can be coated onto a wide range ofsubstrate materials, examples being polymer films such as biaxiallyoriented poly(ethyleneterephthlate) (PET) and biaxially orientedpolypropylene (BOPP); woven and non-woven fabrics; metals and metalfoils such as aluminum, copper, lead, and gold; glass; ceramics; andcomposite materials comprised of laminates of one or more of thesematerials.

The PS of this invention is typically prepared by blending components inany order employing conventional mixing apparatus.

The novel PSA of the invention can be used as a transfer tape. Such atape comprises a support (flexible backing) having coated on at leastone surface thereof a release coating (e.g., silicone, acrylate,urethane, or epoxy material) as is known in the art, the release coatingbeing overcoated with a layer of PSA according to the present invention.

The novel PSA can be used in combination with conventional PSAs(preferably a polar PSA) to afford exceedingly strong bonds betweenplastics and metals. For such uses, an acrylate or other conventionalPSA can be coated onto a release liner and a layer of the novel PSA canbe coated onto the conventional PSA coating. The exposed face of theresulting double-coated transfer tape can be adhered to a nonpolarsupport such as a polyolefin, polypropylene, or polyethylene plasticauto body side molding. Then after stripping off the liner, theconventional PSA coating can bond to metal to provide, for example, thebody side molding of a painted automobile. In another embodiment, thelayers of conventional and novel PSAs can be reversed in position. Inanother embodiment, a desirable result can be achieved by applyinglayers of the novel PSA and conventional PSA to opposite sides of aflexible carrier film which becomes part of the final assembly.

TEST METHODS

The test procedures used in the examples to evaluate and compare theproperties of the PSA compositions and tapes made from them are industrystandard tests. These tests are described in detail in variouspublications of the American Society for Testing Materials (ASTM),Philadelphia, Pa. and the Pressure Sensitive Tape Council (PSTC),Glenview, Ill. References to these standards are also given.

Shear Strength (ASTM D-3654-78; PSTC--7)

The shear strength is a measure of the cohesiveness or internal strengthof an adhesive. It is based upon the amount of force required to pull anadhesive strip from a standard flat surface in a direction parallel tothe surface to which it has been affixed with a definite pressure. It ismeasured in units of time (minutes) required to pull a standard area ofPSA coated sheet material from a stainless steel test panel under thestress of a constant, standard load.

The tests were conducted on adhesive coated strips applied to astainless steel panel such that a 12.7 mm by 12.7 mm portion of eachstrip was in firm contact with the panel with one end portion of thetape being free. The panel with coated strip attached was held in a racksuch that the exposed face of the backing of the strip formed an angleof 182° at the edge of the panel when a 1 kg mass was applied as ahanging weight from the free end of the coated strip. The 2° greaterthan 180° was used to negate peel forces, thus ensuring that only theshear forces were measured to determine the holding power of the tapebeing tested. The time elapsed for each test specimen to separate, i.e.,fall, from the steel panel was recorded as the shear strength.

The time at which the mass fell (average of two specimens) was called"Shear at RT" (when measured at room temperature). When reported as"1000+", the tape had not failed after 1000 minutes. The mode of failurewas indicated as follows:

pp=pop-off, i.e., 75-100% adhesive failure from steel plate

sp=adhesive split leaving greater than 25% residue on each surface

The pop-off failure mode was indicative of adhesive failure of theadhesive/steel interfacial bond as opposed to cohesive failure of theadhesive.

Peel Value [ASTM D 3330-78; PSTC--1 (11/75)]

The peel adhesion was the force required to remove a PSA coated testspecimen from a test panel measured at a specific angle and rate ofremoval. In the examples, this force was expressed in Newtons perdecimeter width (N/dm) of coated sheet. The procedure followed was:

1) A test specimen 12.7 mm wide was applied to a horizontally positionedclean glass test plate. A 2.2 kg rubber roller was used to press a 12.7cm length of specimen into firm contact with the glass surface.

2) The free end of the specimen was doubled back nearly touching itselfso the angle of removal was 180°. The free end was attached to theadhesion tester scale.

3) The glass test plate was clamped in the jaws of tensile testingmachine which moved the plate away from the scale at a constant rate of2.3 meters per minute.

4) The scale reading in Newtons ("Peel Value") was recorded as the tapeis peeled from the glass surface.

Extractables

A square test specimen containing 0.4±0.01 g of PSA was cut from a tapeand placed in a 120-mesh stainless steel basket measuring approximately4×8 cm. The contents were weighed to the nearest 0.1 mg and thenimmersed in a capped beaker containing sufficient toluene to cover thespecimen. After extraction for 24 to 48 hours, the basket (containingthe specimen) was removed, drained, and placed in a vacuum oven at 60°C. The basket and specimen were dried to a constant weight, and the %extractables were determined as follows: ##EQU1## For the tackifiedpressure-sensitive adhesive tapes, the weight of the resin wassubtracted before calculating the corrected % extractables as follows:##EQU2## Two specimens of each tape were tested and average values arereported.

This invention will be further illustrated by the following examples,although it will be understood that these examples are included merelyfor purposes of illustration and are not intended to limit the scope ofthe invention. Unless otherwise indicated, all parts are by weight.

EXAMPLE 1

A PSA composition of 99.5 parts of 1-hexene-co-1,7-octadiene copolymer(98:2 mole ratio), part (a), 0.5 part of the above-identifiedhydrosiloxane crosslinker (1) wherein n'=35, and R is methyl, (part b),and 1.25 parts of 2-ethylhexyl maleate, an inhibitor, included toprevent the room temperature cure of the composition, were dissolved in300 parts of toluene. A pressure-sensitive adhesive composition(approximately 33% nonvolatiles) was obtained by addingbis(divinyltetramethyldisiloxane)- platinum(0) as a thermalhydrosilation catalyst, part (c), to this mixture in an amountsufficient to give 100 ppm of platinum based on the combined quantity ofpolyolefin and siloxane. The polymer solution was then coated onbiaxially oriented poly(ethyleneterephthate) backing using a hand spreadcoater (dry coating weight was 3.8 mg/sq cm). The solvent was evaporatedat room temperature, and the hand spread was heated at 150° C. for 5minutes to ensure complete cure (probably curing for one minute at thattemperature would be sufficient).

The resulting tape had a "Peel Value" of 9 N/dm on glass and a "Shear atRT" of 52 min. with the mode of failure being pop-off. Extractables wereless than 5 percent. A control tape was made in a similar manner, exceptomitting the hydrosiloxane crosslinker and inhibitor and the heatingstep. The control tape had a "Peel Value" of 16 N/dm and a "Shear at RT"of 1 min. with adhesive split.

EXAMPLE 2-5

Four PSA tapes were made in the same way as that of Example 1, exceptthe PSA composition was modified as indicated in Table I which alsoreports test results.

EXAMPLE 6

To the polymer solution prepared in Example 1 was added 33 phr (partsper hundred parts of polyolefin) of Wingtack™ 115 tackifying resin and50 ppm of the platinum catalyst of Example 1 (based on the combinedweight of the adhesive and the crosslinker). A tape was cured as inExample 1. The cured tape had a "Peel Value" of 16 N/dm and a "Shear atRT" of 239 min. with pop-off failure as compared to an uncured tapewhich had a "Peel Value" of 65 N/dm and a "Shear at RT" of about 9 min.with cohesive failure. The percentage extractables after correcting forthe resin was less than 3 percent.

EXAMPLE 7-16

A series of PSA tapes were made in the same way as that of Example 6,except the PSA composition was as indicated in Table I, which indicatesthat in some of the tapes the amount of tackifying resin was varied, andin some cases the tackifying resin was changed to Regalrez™ tackifyingresin. The test data show a significant increase in the internalstrength (shear) of the adhesive when the amount of tackifying resin wasincreased with the mode of failure being pop-off. PSA compositionshaving peel values in the range of 3 to 29 N/dm can be useful in tapessuch as for medical or surgical applications and in insulating tapes.

COMPARATIVE EXAMPLES C-1 through C-5

A series of tapes were made as in Examples 1-16, except the compositionwas modified by omitting the hydrosilane crosslinker and platinumcatalyst and adjusting the tackifying resin as indicated in Table I. Thetest data show that the uncrosslinked adhesives have poor internalstrength (shear).

                  TABLE I                                                         ______________________________________                                             Poly-                 Pt    Peel                                              mer     Tacki-  Cross-                                                                              cata- value                                             system  fier    linker                                                                              lyst  (N/   Shear at RT                            Ex.  (%)     (phr)   (%)   (ppm) dm)   (min) (MOF)                            ______________________________________                                        1    99.5    --      0.5   10     9     52   pp                               2    99.5    --      0.5   50     6     98   pp                               3    99.5    --      0.5   100    3    114   pp                               4    99.8    --      0.2   50     8    198   pp                               5    99.8    --      0.2   100    6    240   sp                               6    99.5    A(18)   0.5   50    16    239   pp                               7    99.5    A(18)   0.5   100   24    265   pp                               8    99.9    A(18)   0.1   100   29    106   pp                               9    99.5    A(33)   0.5   10    15    544   pp                               10   99.5    A(33)   0.5   50    11    283   pp                               11   99.5    A(33)   0.5   100    9    1957  pp                               12   99.5    B(33)   0.5   50    15    1768  pp                               13   99.5    B(33)   0.5   100    9    3800                                   14   99.5    B(33)   0.5   50    27    1786  pp                               15   99.5    B(33)   0.5   100   24    805   pp                               16   99.1    B(33)   0.1   50    23    2844                                   C-1  100     --      --    --    28     6    sp                               C-2  100     A(18)   --    --    55     5    sp                               C-3  100     A(33)   --    --    65     9    sp                               C-4  100     B(18)   --    --    51     10   sp                               C-5  100     B(33)   --    --    62     8    sp                               ______________________________________                                         A = Wingtack ™ 115 tackifing resin                                         B = Regalrez ™ 1126 tackifing resin                                        MOF = mode of failure                                                         pp = popoff (adhesive failure)                                                sp = split (cohesive failure)                                            

EXAMPLES 17-22

A series of PSA tapes were made using the procedure and materials ofExamples 1-16, except the starting α-olefin copolymer was1-octene-co-1,7-octadiene (97:3 mole ratio). See Table II.

COMPARATIVE EXAMPLES C-6 to C-9

Four PSA tapes were made as in Examples 17-23 except the PSA compositionwas modified by omitting the hydrosilane crosslinker and platinumcatalyst (see Table II, below).

EXAMPLE 23

Into 150 ml of toluene was dissolved 23.0 g of 1.2 mole % maleated 60hexene-co-40 propylene copolymer that had been prepared as described forPolymer No. 12 in copending patent application U.S. Ser. No. 07/585,227by the reaction of 60 hexene-co-40 propylene copolymer with maleicanhydride. The solution was refluxed under nitrogen, distilling offabout 20 ml of toluene to ensure removal of water, and 0.23 g of allylisocyanate was added. Refluxing was then continued for three hours.Spectral analysis confirmed the fact that the resulting polymer hadessentially the structure of formula II in which R¹ was C₄ H₉, R² wasCH₃, R³ was H, R⁶ was CH₃, R⁷ was allyl, x was about 450, y was about290' z, was zero, and z" was about 8.9.

The maleated solution was reduced in volume to a coatable viscosity, andcrosslinker, catalyst and stabilizer were added as described inExample 1. The polymer solution was then coated, dried, cured andevaluated as described in Example 1. The results are given in Table II.

                  TABLE II                                                        ______________________________________                                             Poly-                 Pt    Peel                                              mer     Tacki-  Cross-                                                                              cata- value                                             system  fier    linker                                                                              lyst  (N/   Shear at RT                            Ex.  (%)     (phr)   (%)   (ppm) dm)   (min) (MOF)                            ______________________________________                                        17   99.5    --      0.5    50    7     1    pp                               18   99.5    --      0.5   100    4     3    pp                               19   99.5    A(33)   0.5    10   16     17   pp                               20   99.5    A(33)   0.5   100   34     17   pp                               21   99.5    B(33)   0.5    10   15    110   pp                               22   99.5    B(33)   0.5   100   28    120   pp                               23   99.5    --      0.5   100   32    600+  --                               C-6  100     --      --    --    15    <1    sp                               C-7  100     A(33)   --    --    80     1    sp                               C-8  100     B(33)   --    --    77     2    sp                               C-9  100     --      --    --    65    240   sp                               ______________________________________                                    

The data show that PSA tapes of Examples 17-23 are superior to thecomparatives, particularly in the mode of failure. The PSA of thecomparative tapes failed cohesively, whereas the PSA of the tapes of theinvention had greater internal strength.

EXAMPLES 24-34

A series of PSA tapes were prepared as described in Example 1, exceptthat 1-hexene-co-1,7-octadiene (97:3 mole ratio) copolymer was used aspart (a), 0.5 to 2.2 percent of a crosslinker defined in Table III wasused as part (b), and 100 ppm of a photoactive hydrosilation catalystidentified in Table III was used as part (c), and the coated substratewas cured by exposing it to UV radiation (300 mJ/cm²) followed byheating at 100° C. for 2 min. Peel and RT Shear data obtained for eachtape are recorded in Table III.

Shear values varied considerably depending on the choice of crosslinker,catalyst and tackifier. The tape of Ex. 33, in which crosslinker (4),where R is methyl and m is 18, the catalyst [η⁵-(trimethylsilyl)cyclopentadienyl]trimethylplatinum and Regalrez™ 1126tackifier were used, had a shear value of 9344 minutes, while the tapeof Ex. 27, in which crosslinker (1), where n' is 35 and R is methyl, thecatalyst platinum(II) acetylacetonate, and Regalrez™ 1126 tackifyingresin were used, had a shear value of only 900 minutes. Somecombinations of crosslinker and catalyst, however, had good shearvalues, e.g., 1005 minutes (Ex. 32), even without tackifying resin.

                  TABLE III                                                       ______________________________________                                        PSA composition (parts)                                                                             (c)                                                          (a)      (b)     Cata- Tack-                                                  Co-      Cross-  lyst.sup.b                                                                          ifier.sup.c                                                                         Peel                                             Polymer  linker.sup.a                                                                          (100  (33   (N/  Shear                                  Ex.  (%)      (%)     ppm)  phr)  dm)  (min) MOF.sup.d                        ______________________________________                                        24   100      0       0     0     47     6   cf                               25   100      0       0     A     73    16   cf                               26   99.5     D(0.5)  I     B      4   1318  pp                               27   99.5     D(0.5)  J     B      1    900  pp                               28   98.1     E(1.9)  H     0     36     8   pp                               29   98.1     E(1.9)  I     B     52   1185  cf                               30   98.1     E(1.9)  I     C     34   2165  cf                               31   98.1     E(1.9)  J     C     27   6008  cf                               32   98.9     F(1.1)  H     0     26   1005  pp                               33   98.9     F(1.1)  I     B     54   9344  pwr                              34   97.8     G(2.2)  J     B     17   5478  cf                               ______________________________________                                         .sup.a D is crosslinker (1) where n' is 35 and R is methyl                    .sup.a E is crosslinker (3) where Y is 1,4phenylene, R is methyl, and p i     9                                                                             .sup.a F is crosslinker (4) where R is methyl and m is 18                     .sup.a G is crosslinker (5) where Y is phenyleneoxyphenylene and R is         methyl                                                                        .sup.b catalyst H is (η.sup.5cyclopentadienyl)trimethylplatinum           .sup.b catalyst I is                                                          [η.sup.5(trimethylsilyl)cyclopentadienyl]trimethylplatinum                .sup.b catalyst J is platinum(II) acetylacetonate                             .sup.c Tackifier A is Wingtack ™ 115 tackifier resin                       .sup.c Tackifier B is Regalrez ™ 1126 tackifier resin                      .sup.c Tackifier C is Arkon ™ tackifier resin                              .sup.d MOF is mode failure: cf is cohesive failure, pp is popoff, and pwr     is popoff with residue                                                   

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. A pressure-sensitive adhesive comprising acurable blend of an ethylenically-unsaturated α-olefin polymer, acrosslinker having at least 2 hydrosilyl groups, and hydrosilationcatalyst, wherein said ethylenically-unsaturated α-olefin polymer hasthe formula: ##STR14## wherein: x, y, and z are numbers designating therelative molar amounts of M¹, M², and M³ units that are randomly locatedin the backbone chain of the polymer such that the polymer has a weightaverage molecular weight in the range of 30,000 to 3.5 million, x is atleast 60 mole % of x+y wherein y can be zero, and z is 0.1 to 10 mole %of x+y+z;M¹ is an ethanediyl repeat unit of the polymer each having atleast one pendant alkyl group having 4 to 12 carbon atoms; M², whenpresent, is different from M¹, and is an ethanediyl repeat unit selectedfrom 1) ethylene, 2) units having a pendant hydrocarbyl group selectedfrom linear or branched alkyl groups having 1 to 18 carbon atoms, andcyclic and aryl pendant groups having 5 to 18 carbon atoms, and 3)1,2-cyclopentylene and 1,2-cyclohexylene groups having 5 to 18 carbonatoms; and M³ is an ethanediyl repeat unit having a pendantethylenically unsaturated aliphatic or aryl group selected from thegroup consisting of 1) linear and branched mono- and polyethylenicallyunsaturated hydrocarbyl groups having 3 to 18 carbon atoms, 2) cyclicmono- and polyethylenically-unsaturated aliphatic groups having 5 to 18carbon atoms, 3) aryl groups substituted by mono- orpolyethylenically-unsaturated groups having a total of 7 to 18 carbonatoms, and 4) cycloalkenylene groups having 6 to 18 carbon atoms,wherein the cyclic group has at least 6 carbon atoms in the ring,provided that the ethylenically-unsaturated moiety ##STR15## is notbonded directly to a backbone carbon atom.
 2. The pressure-sensitiveadhesive as defined in claim 1 wherein the ethylenically-unsaturatedα-olefin polymer comprises units of the formula: ##STR16## wherein R¹ isan alkyl group having 4 to 12 carbon atoms;R² is hydrogen or ahydrocarbyl group; R³ is hydrogen or R³ together with R² and the carbonatoms to which they are attached is in a saturated monocyclic orpolycyclic ring system having 5 to 20 carbon atoms, wherein at least 5carbon atoms are in the ring system; x, y, z' and z" are numbersdesignating the relative molar amounts of monomer units comprising thebackbone chain of the polymer such that the polymer has a weight averagemolecular weight in the range of 30,000 to 3.5 million, x is at least60% of x+y wherein y can be zero, z'+z" is 0.1 to 10% of x+y+z'+z", andeither z' or z" can be zero; R⁴ is an unsaturated aliphatic hydrocarbylgroup having 3 to 18 carbon atoms, the unsaturated group of which isseparated from the --CH--CH-- of the α-olefin polymer backbond by atleast one carbon atom; R⁵ is hydrogen or R⁵ together with R⁴ and thecarbon atoms to which they are attached is an unsaturated ornon-conjugated polyunsaturated monocyclic ring system having 6 to 20carbon atoms, the unsaturated groups of which are separated from the##STR17## of the α-olefin polymer backbone by at least one carbon atom;R⁶ is a linear or branched alkyl group having 1 to 18 carbon atoms or acyclic alkyl group having 5 to 18 carbon atoms; and R⁷ is a linear orbranched ethylenically or non-conjugated polyethylenically-unsaturatedaliphatic hydrocarbyl group having 3 to 18 carbon atoms or a cyclicethylenically or non-conjugated polyethylenically-unsaturated aliphatichydrocarbyl group having 5 to 18 carbon atoms.
 3. The pressure-sensitiveadhesive as defined in claim 2 wherein R¹ is an alkyl group containingfrom 4 to 8 carbon atoms and R² is H or an alkyl group containing from 4to 8 carbon atoms.
 4. The pressure-sensitive adhesive as defined inclaim 2 wherein at least one of R¹ and R² is an alkyl group containingfrom 9 to 12 carbon atoms.
 5. The pressure-sensitive adhesive as definedin claim 1 wherein the ratio of x and y groups to z groups is from 20:1to 200:1.
 6. The pressure-sensitive adhesive as defined in claim 1wherein the T_(g) of the α-olefin polymer is at most -20° C.
 7. Thepressure-sensitive adhesive as defined in claim 1 wherein the α-olefinpolymer has an inherent viscosity in toluene in the range of 0.5 to 5dl/g.
 8. The pressure-sensitive adhesive as defined in claim 1 whereinthe hydrosilane crosslinker has the formula ##STR18## wherein each R isan alkyl group having 1-6 carbon atoms or a phenyl group,each R¹ is thesame as R or hydrogen, Y is oxygen, an arylene group, an alkylene group,or (CF₂)_(d) where d is an integer from 2 to 10, each m, n and p is 0 ora number in the range of 1 to 35, and at least two R' groups arehydrogen.
 9. A pressure-sensitive adhesive as defined in claim 1 whereinthe hydrosilane crosslinker has the formula ##STR19## wherein n' is anumber in the range of 2 to 35, and R is as defined above.
 10. Apressure-sensitive adhesive as defined in claim 1 wherein thehydrosilane crosslinker has the formula ##STR20## wherein m' is at leastone, n' is a number in the range of 2 to 35, and R is as defined above.11. A pressure-sensitive adhesive as defined in claim 1 wherein thehydrosilane crosslinker has the formula ##STR21## wherein p' is a numberin the range of 2 to 35, and R and Y are as defined above.
 12. Apressure-sensitive adhesive as defined in claim 1 wherein thehydrosilane crosslinker has the formula ##STR22## wherein m is a numberin the range of 0 to 35, and R is as defined above.
 13. Apressure-sensitive adhesive as defined in claim 1 wherein thehydrosilane crosslinker has the formula ##STR23## wherein R and Y are asdefined above.
 14. A pressure-sensitive adhesive as defined in claim 1wherein the concentration of said crosslinker is in the range of 1-20parts per hundred of ethylenically-unsaturated α-olefin polymer.
 15. Apressure-sensitive adhesive as defined in claim 1 wherein the amount ofhydrosilation catalyst is present in an amount in the range of 0.1 to1,000 parts per million of total ethylenically-unsaturated α-olefinpolymer plus crosslinker.
 16. The pressure-sensitive adhesive as definedin claim 1 further comprising a tackifier.
 17. The pressure-sensitiveadhesive according to claim 15 wherein said catalyst is a platinum- orrhodium-containing catalyst.
 18. The pressure-sensitive adhesiveaccording to claim 15 wherein said catalyst is a thermal catalyst. 19.The pressure-sensitive adhesive according to claim 15 wherein saidcatalyst is a photocatalyst.
 20. The pressure-sensitive adhesive asdefined in claim 15 wherein the catalyst is selected from chloroplatinicacid, chloroplatinic acid-olefin complexes, chloroplatinicacid-vinylsiloxane complexes, and platinum supported on amicroparticulate carrier.
 21. The pressure-sensitive adhesive as definedin claim 17 wherein said catalyst is [η⁵-(trimethylsilyl)cyclopentadienyl]trimethylplatinum, (η⁵-cyclopentadienyl)trimethylplatinum, or platinum(II) acetylacetonate.22. The pressure-sensitive adhesive according to claim 1 which has beencured.
 23. The pressure-sensitive adhesive according to claim 1comprising as said copolymer 1-hexene-co-1,7-octadiene, as saidcrosslinker ##STR24## wherein n'=35 and R is methyl, and as saidhydrosilation catalyst bis(divinyltetramethyldisiloxane) platinum(O).24. The pressure-sensitive adhesive according to claim 1 wherein thecyclic mono- or polyethylenically-unsaturated group of M³ comprises atleast one of oxygen and nitrogen heteroatoms.